1. Field of the Invention
The present invention relates to radiographic apparatuses and methods for controlling radiographic apparatuses. In particular, the present invention is suitably used to obtain an intensity distribution of radiation that has passed through an object in the form of a radiographic image.
2. Description of the Related Art
In an existing technique, an object is irradiated with X-rays from an X-ray irradiation source (X-ray generation apparatus), and an X-ray image, which represents an intensity distribution of the X-rays that have been transmitted through the object, is digitized. The digitized X-ray image is then subjected to necessary image processing to thus obtain a clearer X-ray image. In a digital X-ray imaging apparatus and an X-ray imaging system that generate such X-ray images, the X-ray imaging apparatus communicates with the X-ray generation apparatus in synchronization with each other. The X-ray imaging apparatus transmits obtained X-ray image data to an image processing apparatus such as a personal computer to have image processing be carried out on the X-ray image data or to have the X-ray image data be stored in the image processing apparatus. The image processing apparatus causes the X-ray image data that has been subjected to the image processing to be displayed in a display device such as a display.
Typically, the X-ray imaging apparatus is connected with the image processing apparatus and the X-ray generation apparatus by using a general purpose unshielded twist pair (UTP) cable or the like through respective interfaces necessary for the stated apparatuses to be interconnected. In addition, for the purpose of enhancing ease of installation, facilitating handling, and increasing flexibility in capturing images, the aforementioned apparatuses are connected, in an increasing number of instances, through wireless interfaces such as a wireless LAN with IEEE 802.11 being a representative example.
An X-ray imaging apparatus and an X-ray imaging system that can be installed and handled more easily are being implemented. In such X-ray imaging apparatus and X-ray imaging system, the X-ray imaging apparatus itself can detect the start of irradiation with X-rays from the X-ray generation apparatus, making it unnecessary to connect the X-ray imaging apparatus with the X-ray generation apparatus.
There is a method in which the X-ray imaging apparatus successively selects scanning lines in the X-ray imaging apparatus and stands by while switching between an on state and an off state of a two-dimensional sensor. The X-ray imaging apparatus then detects the start of X-ray irradiation by detecting a change in a current that flows inside the X-ray imaging apparatus. According to this method, part of an electric charge produced through X-ray irradiation may flow out in a pixel that corresponds to a scanning line on which the scan has stopped in response to detecting the start of the X-ray irradiation, and as a result, a linear defect may be produced in a resulting X-ray image. As a countermeasure against such a defect, disclosed is a technique in which the image processing apparatus corrects such a linear defect produced in an X-ray image by using a value of a current that flows inside the X-ray imaging apparatus.
However, for example, in a case in which X-rays emitted from the X-ray generation apparatus are weak or in a case in which large part of the X-rays that have reached the X-ray imaging apparatus has been attenuated by the object and so on, a signal to noise ratio (S/N ratio) of the value of the current that flows inside the X-ray imaging apparatus may be low. In such a case, the value of the current that flows inside the X-ray imaging apparatus may need to be subjected to preprocessing in order to use that value for correcting the defect, and thus processing time therefor may become necessary. In addition, the time it takes to transmit the value of the current that flows inside the X-ray imaging apparatus to the image processing apparatus or the time it takes to carry out correction processing on the X-ray image by using the value of the current that flows inside the X-ray imaging apparatus may also become necessary. Meanwhile, in the X-ray imaging system, there is a high demand for a captured image to be displayed as quickly as possible in order to check the result after irradiating an object with X-rays to capture an image, and the above configuration goes against such a demand.